New IAC didn't work ??

the98stang · Nov 14, 2006

svtpower said:
Dunno what to say, both my 99GT and my 99 Cobra both had the hanging idle issue, and the IAC restrictor worked like a champ for both cars. It definately did not make the issue worse. The IAC is a bypass for the air intake when the TB is closed, decreasing that passage size and allowing less air seems like the logical answer to me...

You may want to clean your TB if you have not already incase it's sticking...

I was told the "grease" in the TB should not be cleaned. Forgot why though

the98stang · Nov 14, 2006

edit:

Direct quote from Kilgore :"Did you remove the TB when you cleaned it? BTW, never clean it. The TB has a sludge resistant, maintenance free coating that is damaged by ANY type of spray cleaner."

svtpower · Nov 14, 2006

lol

the98stang said:
edit:

Direct quote from Kilgore :"Did you remove the TB when you cleaned it? BTW, never clean it. The TB has a sludge resistant, maintenance free coating that is damaged by ANY type of spray cleaner."

riiiiiight. Thats some BS if I have ever heard it. Lots of people use seafoam to clean the intake. The TB should be free of oil buildup to work properly. If you car has more than 60K miles on it and its never been cleaned, its likey dirty.

Mike97gt · Nov 14, 2006

bluextc said:
ok, found out what I need to log and will do so tomorrow and post the results..

LT fuel trims for both banks are the most important when trying to diag a rolling idle. If I remember correctly SCT datalogging uses a whacky scale for long term fuel trim. Our Ford scan tools use a -25 to + 25 scale meaning if you see a + 25 the pcm is adding 25 percent more fuel to the stock mixture.

One thing to keep in mind is this might not be a engine control issue at all. What I need you to do is start the car cold and drive around with the climate control system completely off ( no heat, no a/c only use the OFF pos. ) and see if you still have this rolling idle, if you do not have the problem then you may have a A/C compressor that is short cycling, sometimes this can cause a rolling idle like you are having. The A/C runs in both A/C positions plus the defrost and the mix pos.

The other likely thing it could be is a large vacuum leak, the long term fuel trim readings will tell us that. Most of the time if you have a leak especially one large enough to cause a rolling idle you will get a CEL with codes p0171,p0174. Since you did not say you have these issues I would check a possible climate control concern first.

Kilgore Trout · Nov 15, 2006

svtpower said:
riiiiiight. Thats some BS if I have ever heard it. Lots of people use seafoam to clean the intake. The TB should be free of oil buildup to work properly. If you car has more than 60K miles on it and its never been cleaned, its likey dirty.

YardSpecial · Nov 15, 2006

The coating is clear coat and 3m sells a cleaner the does not hurt it.

If it was not coated the aluminum would corrode like crazy

Fast cleaning action for dirty throttle plates. Can be sprayed upside down. Cleans and lubricates. Safe for coated throttle plates.

View attachment 424070

Kurgan · Nov 15, 2006

svttech76 said:
One thing to keep in mind is this might not be a engine control issue at all. What I need you to do is start the car cold and drive around with the climate control system completely off ( no heat, no a/c only use the OFF pos. ) and see if you still have this rolling idle, if you do not have the problem then you may have a A/C compressor that is short cycling, sometimes this can cause a rolling idle like you are having. The A/C runs in both A/C positions plus the defrost and the mix pos.

My GT was doing this before I had problems with my motor. I was able to identify, with the hood open, that the clutch on the AC compressor was engaging on and off very frequently and coinciding with when my engine's idle was going up to about 2000 RPM.

What's the fix for this?

YardSpecial · Nov 15, 2006

Kurgan said:
My GT was doing this before I had problems with my motor. I was able to identify, with the hood open, that the clutch on the AC compressor was engaging on and off very frequently and coinciding with when my engine's idle was going up to about 2000 RPM.

What's the fix for this?

Sounds like the A/C is LOW on Freon..............

RandyStinchcomb · Nov 15, 2006

Kurgan said:
My GT was doing this before I had problems with my motor. I was able to identify, with the hood open, that the clutch on the AC compressor was engaging on and off very frequently and coinciding with when my engine's idle was going up to about 2000 RPM.

What's the fix for this?

low on freon or a bad A/C cycling switch

Stang|ess · Nov 15, 2006

RandyStinchcomb said:
low on freon or a bad A/C cycling switch

if my car only does it in position 1 and 2, but not 3 and 4, is it more likely the cycle switch?

RandyStinchcomb · Nov 15, 2006

Stang|ess said:
if my car only does it in position 1 and 2, but not 3 and 4, is it more likely the cycle switch?

I can't say for-sure, maybe Mike will have somemore input on this.

bluextc · Nov 15, 2006

Well, I logged all the things requested, but unfortunately won't have a laptop for a few more weeks, so I tried to transfer the info in on the desktop, and can't figure out how to make it work. The car's hot right now, so I can't try that right now, but I will after it cools down. I am pretty sure I am low on freon, because I tried the air once or twice in the summer and didn't get cold air, but since I don't use it (only turn it on for the kids now and then), I didn't care, and was eventually going to do an a/c delete... Maybe this is the problem???

edit: oh, and the tb is new, just put in a couple months ago.

Kurgan · Nov 15, 2006

RandyStinchcomb said:
low on freon or a bad A/C cycling switch

Dangit Randy! Stop tryin to make me order more parts!

I'll wait to see if this still happens when I get the new motor running. Last I remember checking, the A/C was still blowing cold air just fine.

Mike97gt · Nov 15, 2006

RandyStinchcomb said:
low on freon or a bad A/C cycling switch

exactly.. many times it's low freeon, so that means you have a small leak.

Mike97gt · Nov 15, 2006

bluextc said:
Well, I logged all the things requested, but unfortunately won't have a laptop for a few more weeks, so I tried to transfer the info in on the desktop, and can't figure out how to make it work. The car's hot right now, so I can't try that right now, but I will after it cools down. I am pretty sure I am low on freon, because I tried the air once or twice in the summer and didn't get cold air, but since I don't use it (only turn it on for the kids now and then), I didn't care, and was eventually going to do an a/c delete... Maybe this is the problem???

edit: oh, and the tb is new, just put in a couple months ago.

yeah the A/C is your problem then, test it the way i said with the climate control selector in the off pos. and make sur ethe a/c is not cycling. The fix for this is to fix the A/C leak and have it charged or pull the plug on the a/c compressor.

bluextc · Nov 15, 2006

Thank you svttech, I have not been able to drive the car since it cooled down, due to having a drink, but am pretty sure now that it's diagnosed. Can you tell me how to pull the plug on the a/c compressor... and will this affect anything other than the a/c? I really don't care about the a/c at all, but I do want heat...
and thank you for all the help...

blacksheep-1 · Nov 15, 2006

The a/c switch might be adjustable, if the a/c is fully charged, then look into the a/c switch with the plug off. You should see (unless it's aftermarket) a set screw, you can turn that and make some adjustments to the sensitivity of the switch.

FOXtool · Nov 15, 2006

I AGREE WITH SVTPOWER, IVE BEEN WORKING ON CARS FOR YEARS AND I KNOW SOME MANUFACTURES SAY NOT TO CLEAN THE TB- THATS BS. 90% OF THE VEHICELS THAT COME INTO MY SHOP WITH THE "SLUDGE RESISTANT" TB NEED TO BE CLEANED. DONT USE A WIRE BRUSH, USE A LIGHT SOLVENT AND A TOOTHBRUSH. OTHER THINGS YOU NEED TO LOOK FOR THAT CAN CAUSE AN ERRATIC IDLE ARE VACUUM LEAKS, TIMING, AND ALSO DOES YOUR TB HAVE A THROTTLE STOP SCREW? IT COULD BE MISADJUSTED CREATING AN INCORRECT BASE IDLE SETTING.

Mike97gt · Nov 15, 2006

bluextc said:
Thank you svttech, I have not been able to drive the car since it cooled down, due to having a drink, but am pretty sure now that it's diagnosed. Can you tell me how to pull the plug on the a/c compressor... and will this affect anything other than the a/c? I really don't care about the a/c at all, but I do want heat...
and thank you for all the help...

there is a electrical connector on the a/c compressor but thats hard to get to, you can pull the plug off the A/C cycling switch that is located on the A/C accumulator here is a picture of the area where the a/c accumulator is

the accumulator is that round cylinder with the arrow pointed to it.

Don 95Vert · Nov 16, 2006

The coating is NOT there so the inside is sludge resistant - it's there to keep the blade from sticking so the TB blade can be completely shut so the IAC can control idle by itself. Ford spends a LOT of $$ coating them. This is why most aftermarket TBs are bad, they do not have this coating and rely on keeping the TB blade slightly cracked to keep ot from sticking. There are a number of coating safe sprays - and they do need to be cleaned once and a while.

If the vehicle is mostly stock and the idle is surging, there is a problem somewhere. Most likely a vacuum leak. I'd recommend doing a smoke test to find it. BTW: breathers on valve covers with a functioning PCV system are a big vacuum leak.

The other issue is if someone messed with the TB stop screw. That should never, under normal circumstances be messed with. All idle speed is controlled by the EEC and IAC.

The other thing to note, whenever you do something to a component that controls idle, you need to clear the KAM. It'll then re-learn idle settings in about 10 minutes.

With the Xcal 2 log idle air intergrator - shold be very close to "0" and IAC duty cycle, should be 35-45%. If it isn't something else is going on - or your tune in the Xcal needs some work.

Hope this helps, good luck!
Don

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